What a bummer on the mileage. You missed warranty by 2000 miles. I could check your vein though, if you'd like me to see for sure.
Do you happen to know if these codes were also present before these items were replaced?
I suspect that there is a short to ground somewhere in the sensor power circuit. It is also possible that the O2 sensor fuses are blown, so be sure to check them in the underwood fuse block. The short could also be in one of the O2 sensors, but we'll see.
Do you have a 12v test light and a digital multimeter to continue? It would be nice to access a scan tool, but we may be able to get around that issue.
If you don't have either of these, I would suggest at least unplugging each O2 sensor to inspect the terminals. Make sure that none of the terminals have bent over pins or any visible damage. Give each wire a tug also, to see if the wires are damaged internally.
trace the engine harnesses also to look for anywhere that a metal bracket could have rubbed through the conduit and cut into the wires. sometimes wires even stick out of the conduit and get cut that way. Simply pull the harness away from anything suspicious and see if has cut into it. If you see damage, strip down the harness to access and repair the wires.
If these checks don't yield anything and you want to continue with the test light and multimeter, let me know and I'll provide the necessary info.